BQ24700 Datasheet, PDF (21/29 Pages) Texas Instruments – NOTEBOOK PC BATTERY CHARGE CONTROLLER AND SELECTOR WITH DPM

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bq24700, bq24701
NOTEBOOK PC BATTERY CHARGE CONTROLLER
AND SELECTOR WITH DPM
SLUS452B – APRIL 2001 – REVISED NOVEMBER 2002
APPLICATION INFORMATION
compensating the loop
For the bq24700/bq24701 used as a buck converter, the best method of compensation is to use a Type II
compensation network from the output of the transconductance amplifiers (COMP pin) to ground (GND) as
shown in Figure 8. A Type II compensation adds a pole-zero pair and an addition pole at dc.
100 µA
gm
+ ^AMPLIFIER
gm
+ ^AMPLIFIER
COMP
10
CP
RCOMP
CZ
gm
+ ^AMPLIFIER
bq24700
UDG–00118
Figure 8. Type II Compensation Network
The Type II compensation network places a zero at
FZ
+
1
2
p
RCOMP
CZ Hz
(10)
and a pole at
FP
+
1
2
p
RCOMP
CP Hz
(11)
For this battery charger application the following component values: C_Z = 4.7 µF, C_P = 150 pF, and
R_COMP = 100Ω, provides a closed loop response with more than sufficient phase margin.
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